New research in mice shows potential for Alzheimer's and brain trauma treatment. / Robert F. Bukaty, AP

by Karen Weintraub, Special for USA TODAY

by Karen Weintraub, Special for USA TODAY

Children are increasingly surviving childhood cancers, but the treatment leaves many of them unable to have children of their own. Older boys who have reached puberty can have their sperm frozen and banked; younger boys haven't had that option.

Now, a new study in mice suggests it may someday be possible for these younger boys to have a small amount of tissue from their testicles preserved before treatment, defrosted years later and used to generate sperm cells.

Japanese researchers published a paper today in Nature Communications, showing that they could make baby mice from sperm generated this way.

The research still has a long way to go, though, before it can be used in humans, said Takehiko Ogawa, a urologist and scientist at the Yokohama City University Graduate School of Medicine, who led the study.

While it was relatively easy to work with the preserved tissue from mice, human tissue is proving much more difficult, he said. The human tissue does not survive in the same lab conditions that work for the mice, and though he has made several different attempts so far, he is not yet close to producing human sperm, Ogawa said.

"We have to optimize the culture conditions in each species," he said.

In the meantime, Richard Yu, a pediatric urologist with Dana-Farber/Boston Children's Cancer and Blood Disorders Center in Boston, said if he had a son fighting cancer, he'd preserve the boy's testicular tissue now.

"Research in the last few years really is encouraging that the technique will be available in the future," he said. "The alternative is to do nothing and your child has a high risk of sterility."

The promise of fertility preservation is part of a larger effort to reduce the side effects of childhood cancer care, Yu said.

Now that 70% to 90% of children with cancer survive to adulthood, doctors have focused on improving the quality of that life, either by minimizing harmful treatments or by developing strategies like Ogawa's to counter side effects.

"There's just a greater awareness of the issues in the cancer survivors," Yu said.